1. Field of the Invention
The present invention relates to an air-conditioning system which has a capability of computing torque needed to drive a compressor.
2. Description of the Related Art
To suitably control the power of the engine of a vehicle, the torque necessary to drive a compressor which uses the engine as its drive source has generally been computed. For example, the actual torque needed is computed based on the theoretical torque which is theoretically needed for the current drive of the compressor and the loss torque which needs to be considered due to friction or the like in the compressor, and the engine power is controlled based on the computed torque.
Although the loss torque of a compressor differs depending on the operational state of the compressor, it has been treated as a constant value so far without considering the fact. It is therefore unable to accurately compute the torque of a compressor and eventually control the engine power with high precision.
While there is an idea of directly detecting the torque of a compressor by using a torque sensor, the sensor is expensive and requires a large mounting space so that the idea is not practical.
Accordingly, it is an object of the present invention to provide an air-conditioning system capable of accurately computing torque needed to drive a compressor.
(It is another object of the present invention to provide an apparatus for engine control that can accurately compute the torque of an engine which drives a compressor, in accordance with a change in the torque needed to drive the compressor.)
According to one aspect of the present invention, an air conditioning apparatus is provided. The apparatus includes a coolant circuit that has a compressor. A driving status of the compressor is detected by a first detecting means. The apparatus has a first calculating means and a second calculating means. The first calculating means calculates a theoretical torque and a driving efficiency of the compressor based on information from the first detecting means. The second calculating means calculates a necessary torque required for driving the compressor. The second calculating means calculates the necessary torque based on the theoretical torque.
According to another aspect of the present invention, an apparatus is provided. The apparatus controls an engine that is a driving source of a vehicle and an air conditioner mounted on the vehicle. The apparatus comprises the first detecting means, the first calculating means, the second calculating means, and a control means. The first detecting means detects a driving status of the compressor. The first calculating means calculates a theoretical torque and a driving efficiency of the compressor based on information from the first detecting means. The second calculating means calculates a torque required for driving the compressor. The second calculating means calculates the necessary torque based on the theoretical torque. The control means controls the engine reflecting the torque calculated by the second calculating means.